Means for the propulsion of ships



J. J. CCRDOVA MEANS FOR THE PROPULSION 0F -SHIPS Filed June y24, 1941 4 Sheets-Sheet l Joss' JUAN ConovA Dec. 1, 1942. J. J. coRDovA 2,303,437

MEANS Fon THE PRoPULsIoN oF SHIPS Filed June '24, 1941 4vsneets-sheet 2 gmc/YM Jos JUAN CoRpovA De- 1, 1942 J. J. cQRDoVA MEANS VFOR` THE PROPULSION 0F SHIPS Filed June 24, 1941 4 Sheets-Sheet JMW Jos JUAN r(LoRDovA Dec. l, 1942. J, J, cgRDovA I 2,303,437

MEANS FOR TH PROPULSION OF SHIPS Filed .Jima- 24. 1941 4 sheets-sheet 4 Jos JUAN CORDOVA Patented Dec. 1, 1942 UNITED STATES PATENT OFFICE MEANS FOR THE PROPULSION OF SHIPS Jos Juan- Cordova, Buenos Aires, Argentina Application June 24, 1941, Serial No. '399,514

3 Claims.

ous types of hydraulic motors and the factors contributing to their eiciency are considered it is seen that the type having the highest eiciency is the screw turbine, which under favourable conditions gives an eciency in the neighbourhood of 95%. One of the essential conditions for obtaining a high elciency in connection with screw rturbines is that the jet or stream shall be directly projected onto the blades of the screw. Bearing in mind this point, which will be further discussed below, it is found that the screws at present v.

used for propelling ships have a very low elliciency, one of the principal causes of which is the fact that the water against which the blades exert their thrust or into which they may be said to bite is scattered on leaving the screw, whereby a considerable proportion of its propelling power is lost. This statement is supported by the teaching of the textbooks. The loss referred to does not take into account the additional loss due to the resistance offered to the displacement or advance of the vessel. It will therefore be seen that if the scattering of the water behind the screw can be diminished or suppressed, a considerable increase in efciency would result.

The resistance factors which likewise effect the overall eiiiciency of the propulsive system, may be divided into three classes. First the direct or head-on resistance, oiered by the water to the advance of theV vessel. This direct resistance which is proportional to the cross section of the vessel normal to' the water, that is to say to the cross sectional area of the submerged portion of the midship frame, and to the square of the vessels speed, consists of two parts, namely the positive pressure on the leading surfaces, and the negative pressure on the trailing surfaces. The'liquid streamlets or filaments on meeting the obstruction oferedby thevvessel tend to rise on the leading surfaces thereby increasing the submerged area, to an extent depending on the speed, but at 'the trailing end, the streamlets or laments which have been separated by their passage around the vessel do not immediately come together again but join up at a certain distance from the trailing end thus forming a dead space and producing a negative pressure or suction eiect on said trailing end.

The second class is the longitudinal resistance due to the friction of the liquid laments passing alongside the vessel, andY thisv resistance is proportional to the wetted area and to a certain power of the speed.v It is greater than the direct resistance at low speeds, and increases with the roughness of the material or the dirty conditions of the bottoms.

The third class of resistance is that due to the waves which beyond a certain speed are produced in the water and originate both at the stern and at the stem of thevessel. At the Vstem they appear as crests and at the stern as hollows. At rst divergent WavesV and later, transverse waves appear, and these are produced at the cost of a certain amount of energy produced by the vessel. The transverse waves aiect the direct resistance, and cause the latter to increase or diminish according as the crests or hollows of the transverse waves formed at the bow correspond to the hollows of the waves originated at the stern, Iby reason of the greater or less negative pressure which they produce at that position. This class of resistance is calculated as proportional to the fourth power of the speed.

The unbalancing effects of these factors are best seen in small high speed vessels, such as those commonly known as ,speed boats,V the bows of which rise to a considerable extent from the water, whereas their sterns tend to go down.

Naval designers have at a1l times sought to damp out these resistances by increasing the trimming coefficients, but it may be said, that although possibly the maximum efficiency has been reached -by the successive evolutions of the under water body, the line above indicated is not exactly the proper one to follow in order to neu'- tralisesaid resistances. To sum up this part of the discussion, it may be said that attempts have been made to damp out the said resistances, the

ideal solution would have been a method of neutralising them.

A further source of energy lost is the rolling and/or pitching of the vessel, due partly to the combined unbalancing eiect of the above mentioned resistances and partly to the efect of the natural motion'and waves of the wateror sea. The pitching may lbe so pronounced that in heavy seas the screw may be entirely out of the water for'appreciable periods, and this fact represents not only a loss of speed and efciency by reason ofl the interruption of the propulsion eiect, but also places a heavy strain on the engines. In this connection, mention may be made of the additional disturbing motion to which warships are subject when in action due to the recoil on ring their guns.

At present'the stability of a surface vessel is practicallyventirely dependent on the design of its under water body. Insome instances attempts have beenmade to increase the stability by the use of gyroscopic devices, but they have not been found to be very eifective.

In submarines, the resistance offered by the `water to displacement, when the vessel is submerged, is greater at lower spreeds than when the vessel is aoat by reason of the increase in the submerged cross section perpendicular to the direction of motion. Similarly, owing to the increased surface wetted by the water the tangential frictional resistance increases. It should be noted, however, that in the case of l,under water 'craft travelling submerged, they do not give rise to the diverging and transverse Waves referred to above.

From the foregoing it will be seen that the resistance advantage of surface over submergedunder water craft at low speeds is gradually offsetas the speed increases by the increase in the resistance factor represented by the divergent and transverse wavesV which are perculiar to surface craft, so that eventually a point is reached at which the total resistance for both types of vessel is the same, and beyond which the resistvance of the surface vessel is greater than that of the submerged under water craft, said point depending on the type of vessel and its draft. These facts clearly bring out the very considerable importance of the resistance to motion arising from the aforesaid waves, and lead to the 'conclusion that very desirable high speeds could be obtained if the factor introduced by said waves could be eliminated.

In under water craft when submerged the stability depends entirely on the weight distribution, since the longitudinal and lateral stabilities are equal and of substantially Zero value, whereby free movement on board is hindered -with the resulting inconvenience for the crew and a reduction of their service efciency. The importance of this stability question may be seen from the fact that a change in position of a single man on board over a distance of a few metres vwill cause a very considerable increase in his effective weight and may produce an inclination or list dangerous to the submerged vessel. For example, in a Vickers type 400 ton submarine which has a submerged metacentric height of only 15.3 the displacement from abaft to forward of a pair of men having a total weight of 150 kg. would, over a distance of 30 m. produce an increase of 4,500 kg. in effective weight, and therefore, would produce an inclination of the vessel of 4 12. In a submarine of thesame displacement built by the Electric Boat Co., having a metacentric height of 35.6, the inclination under the 'same conditions would be 1 49', and at a speed of miles an hour. the Vickers type vessel would plunge to a further depth of 22.5 m., whereas the Vsecond type of vessel mentioned would plunge 9.75 m., both vessels thus reaching depths which would be dangerous.

The principal object of the present invention is to provide a method and means for the propulsion of surface and under water craft whereby the above mentioned disadvantages and objections shall be overcome.

A further object of the present invention is to Iprovide a method and means for the propulsion of surface and under water vcraft in which the active element is a turbine screw.

Another object of the present invention is to provide a method and means for the propulsion of surface and under water craft, in which the active element is a turbine screw arranged within a duct extending lengthwise of the vessel,

whereby said turbine screw is caused to actI on from the corresponding equation..

' posed.

a confined body of water discharged at the trailing end of said duct substantially without scattering.

A further object of the present invention is to provide a method and means for the propulsion of surface and under water craft comprising the utilisation of a plurality of turbine screws disposed in series in a water confining duct extending lengthwise of said vessel divisible into compartments by normally open watertight doors whereby-the interior of said duct may be isolated from the water and evacuated to permit of access to said turbine screws for inspection or repair.

These and other objects and advantages of the present invention will become apparent in the course of the following description of certain embodiments thereof diagrammatically illustrated in the accompanying drawings in which Fig. 1 is a diagrammatic plan partly in section of a vessel provided with my novel propulsion means.

Fig. 2 is a diagrammatic side elevation of the bows of a vessel adapted to be propelled by the novel means according to the present invention, illustrating the intake of a water duct.

Fig. 3 is a diagrammatic plan of the stern of a vessel with improved propulsion means according to the present invention showing the arrangement of the rudders.

Fig. 4 is a section on the IV-IV of Fig. 1 il- 'lustrating a method of driving the propeller ing the effect of tilting the diving fins of the arrangement of Fig. '7.

Fig. 9 is a plan showing diagrammatically an alternative application of the principles of the present invention, and

Fig. 10 is a diagrammatic plan illustrating an alternative embodiment.

With reference to Fig. 1 a surface vessel I0 is provided according to the present invention with a pair of ducts I2, I2 symmetrically disposed about the longitudinal centre line of the vessel. In the embodiment shown in Fig. 1 the ducts I2, I2 are provided within the confines of the hull I4 and communicate with the surrounding water by means of enlarged intakes I6, I 6 provided vin the bows I8 and preferably protected by a Ysymmetrically disposed parallel to the centre line of the ship, but spaced outwardly therefrom. TheV odd duct, if any, would be centrally dis- It should be noted that it is desirable to locate the symmetrically disposed ducts as near to the outer coniines of the hull as possible so as to enhance the various advantageous effects hereinafterl explained.

At the stern end of the vessel the ducts are preferably continued in the form of tubular extensions beyond the connes of the hull I4 to form parallel outlets 26, 26 which, as indicated in Fig. 3, are preferably located so as to discharge the water against the rudders 23, 28. From the point at which a duct l2 merges with the ntake IG it may be of the same diameter throughout down to the outlet 255, or the diameter of the duct may be gradually reduced in order to obtain the discharge pressure considered necessary.

Within each duct I2 are provided a plurality of turbine screws Si! mounted each on a shaft 32 rotatably supported in bearings 34 suitably suspended or supported centrally of said duct as by arms 3%. Each shaft il? is adapted to be driven from the vessels engine in any suitable manner. For example, as shown in Figs. 4 and 5 the shaft 3i.' may be driven by conical gearing comprising a driven member 38 fast on the shaft 32 and a driving pinion lili fast on a transmission shaft d2 extending along the bore i4 of one arm 36d supporting the bearing structure 3d. The transmission shaft fill is conveniently supported by bearings it disposed at spaced points within the bore lid. According to one aspect of the invention, certain advantages, which will hereinafter be more particularly described, may be obtained by using variable pitch screws Sco, (Fig. and in that event the pitch control rod 48 may conveniently extend through a passage 5u formed within the arm a through which the transmission shaft #l2 passes. By this arrangement it is possible to enclose a driving mechansin ier the shaft 3L in a watertight structure while at the same time maintaining the obstruction of the ovv of water through the duct I2 at a minimum.

As will be readily appreciated from what has been stated hereinabove the ducts I2, l2 will be located so as to be permanently below water level whatever the lo-ad on the vessel, whereby to ensure that the eiective portion of the ducts, in which the screws 3@ are installed, and which extend from the point of mergenoe with the intake i6 it to the extremity of the outlet 25, 26', is Linder running conditions completely lled with water.

The screw nearest the bows in any one duct l2, hereinafter the leading screw and diierentiated in the drawings by the reference character 3S acts as suction screw to positively draw in water through the intake I5 into the duct I2 and positively drive said water towards the subsequent screws Si). The water drawn into the duct I2 may be said to be piped and thus protected from external disturbances, so that being subjected only to the action of the screws the body of water contained within the duct I2 ac- Iduires very' uniform rotary and translational motions so that it acts from one point of view, very much like a rotating rod oi similar diameter. Consequently said body of water, which is of course constantly streaming through the duct I2, but which may at any given moment be considered as a rotating mass extending from the neighbourhood oi the leading screw to the outlet has a considerable moment of inertia. Owing to the presence in the duct of the rotating screws gyroscopic elrects are also obtained when said screws are symmetrically disposed about the centre ofgravity. Both these features contribnte to augment in a very high degree the stability of the vessel to any of the disturbing factors previously described. This stabilising action is particularly pronounced in the case of submerged under water craft and the important advantages to be derived therefrom will be readily appreciated from the foregoing discussion.

The leading screw drives the rotating body of water towards the next screw 38, said body of water having a considerable kinetic energy, so that if the second screw were free to rotate it would be driven by said rotating body of water as a turbine and could transmit energy with an efliciency of approximately As previously stated, however, said second screw is operatively coupled to be driven from the ships engine in order to exert an additional thrust on the body or column of water and in turn deliver the water with increased kinetic energy to the next screw. Owing to what may be called a turbine eiect ci the column of water due to the rotation impressed upon it by the leading screw, a very small eort is required at the second screw to increase the force received and to deliver the water with increased kinetic energy to the next screw. Moreover, if the above result is to be achieved, it will be clear to those skilled in the art that the individual rotational speeds of successive screws must increase from bow to stern. Furthermore, the angles of incidence of the blades must decrease for successive screws from bow to stern. The first screw must have a relatively louT speed ci rotation on account of the greater effort it is called upon to maire in order to pull the water into the duct and cause it to rotate The next screw requires a smaller angle of incidence at a higher speed since it has delivered to it a piped body of water in a state oi whirling motion and having' a high kinetic energy. The relative proportions of angles of incidence and rotational speeds will have to be correctly calculated to suit the type of vessel and the H. P. of its engines so that the maximum eiiiciency of the screws and a rational distribution of effort may be obtained.

It will, therefore, be seen that according to the present invention, the vessel is propelled by turbine screws acting on a confined body or column of water whereby the maximum thrust eiiciency is obtained. Moreover, the rapidly whirling column of water on issuing from the outlets 26 of the ducts i2 exerts a positive thrust upon the body of water in the wake of the vessel. The improvement thus obtained is itself worthy of consideration since by the new method the effect of back pressure at the trailing end of the vessel is substantially neutralised. However, `a much more important consequence of the arrangement is due to the fact that the water is sucked or drawn into the enlarged intakes i6 situated on either side of the bows. This sucking in of the water prevents the rise of the water against the bows, which normally takes place when the vessel is sailing, and moreover avoids the necessity for causing the bows to thrust or cut through the water because the water ahead oi the vessel is drawn aside into the intakes i6, I6 thereby eliminating or at least very considerably reducing the most important of the three resistance factors hereinbefore explained. This reduction in resistance is due to the fact that the piped body of water moves through the ducts at a higher displacement speed than that of the vessel, that is to say than the relative speed past the vessel of the main body of water, and said` piped body is subjected only to the comparatively low frictional resistance of the duct, while at the sides of the vessel only the longitudinal frictional resistance is developed, which can. naturally, never be completely eliminated. Thus the novel method of propulsion according to the present invention suppresses or neutralises two of the three resistance factors, namely, the direct or head-on resistance and the back pressure resistance leaving only the longitudinal frictional resistance which although it cannot be entirely eliminated, may be considerably reduced by modern streamline design. In this connection, attention may be drawn to the fact that the present invention will enable considerable improvements to be made in stern designs.

For reasons similar to those advanced in connection with the elimination of the head-on resistance, the resistance effect of the diverging and transverse waves is also eliminated. Thus apart from other advantages, such as increased stability and maneuvering power, as will be more fully explained hereinafter, the novel method of propulsion allows of a very more efficient utilisation of the engine power and also allows considerably higher speeds for the same power to be achieved in both surface and under water craft, owing to the more efficient conditions under which the screws are made to work and to the elimination of the head-on resistance. The advantage thus gained may be utilised to reduce the dead weight of the engines and increase the space available for stowage and other purposes, or used to increase the radius of action of the vessel, or else a compromise solution may be adapted. The possibility thus made available of reducing the dead weight of the engines, may be turned to particular advantage in warships, the armouring of which may thus be considerably `strengthened without in any way reducing the range of action or the ease of handling as compared with present day standards. Alternatively of course, the armament of the vessel may be increased.

As has already been indicated, the ducts i2,

are preferably adapted to be divided into sec.

tions, as by means of normally opened watertight doors indicated at 52 in Fig. 1. Of these one will be provided at each end of the duct beyond the portion thereof in which the screws are located and preferably one such door will be provided behind each screw or between each pair of screws. The purpose of such water tight doors is to shut oi the interior of the duct from the surrounding water and thus permit the duct to be drained, by expelling the water from the closed duct, as by compressed air, bilge pumps or the like, in order to permit of access to the duct for purposes of inspection and/or repair of the screws or their immediate driving mechanism, without the necessity of putting the ship into dry dock. The evacuation of the ducts I2 may be utilised for other purposes, very conveniently as will be further explained below with under water craft.

The protecting grids 2D may conveniently be constructed of flexible material and made up in removable sections to allow for ease of cleaning, repair and replacement. Preferably the securing frames 22 are located so that the pressure of the water is taken up by the hull structure, as indicated in the drawings, whereby strain on the fixing bolts is avoided.

Although in Fig. l the frames 22 have, for the sake of clearness, been shown as simply superposed on the outer surface ofthe hull, I1t 1s bows, all the screws in the other duct l2 will be caused to rotate in the other direction, that is, counterclockwise on the port side when looking aft from the bows. In this way not only is a steady and uniform forward motion oi the vessel insured, but all tendency to careening or heeling is avoided, and moreover a very high levelling or stabilising effect is obtained owing to the action ,of the columns of water.

It should be clearly understood that said columns of water have a twofold eiect. On the one hand by their translational iiow through the confining ducts, they act as rigid bodies of high moment of inertia and thus tend to stabilize the vessel and resist forces tending to cause pitching and the like. This stabilizing effect is, to some extent proportional to the transverse separation of the ducts. On the other hand, the piped body of whirling water leaving the duct enables a very high thrust to be exerted on the main body of water in the wake of the ship. It should also be noted that, whereas xed pitch screws may be used, it is preferred to use screws of variable blade pitch for the reason that such screws enable a more accurate interadjustment to be achieved and losses in eciency avoided. The advantage of variable pitch screws arranged to be controlled from within the ship will readily be appreciated if it be remembered that the pitch and speed of rotation of the successive screws must differ, as explained above, in order to ensure that each screw shall contribute an increment of energy to the column of water passing through the duct.

Although the invention has so far been described on the assumption that two parallel ducts are provided symmetrically disposed about the ships centre line and built into the structure of the hull, it is clear that a single central duct |2a may alternatively be provided with eiiicient results. It is also within the scope of the present invention to provide the ducts outside the hull structure proper as shown at |2b and l2b in Fig. 11. Obviously the stabilising effect and the maneuvering possibilities will be greater if twin ducts are provided.

Considering now the other advantages to be derived from the new method of propulsion, one of the most evident of these is the counteraction of the effect of high seas and ground swell by the stabilising properties of the columns of water passing through the ducts and the gyroscopic eiect of the screws. The moment of inertia .of said columns which is proportional to ment of the duct. This equivalence to a supporting plane is irrespective of the gyroscopic action of said screws.

The stabilising effect of the column of water passing through the ducts while of considerable importance and advantage in surface craft, is of very considerable importance in connection with under water craft, in which as hereinbefore explained, there is little if any stability when the vessel is submerged. Hence the application of the present invention to submarines will very considerably improve the stability of the vessel when submerged thereby permitting a much greater freedom of movement on board. Moreover the reduction in dead weight which can be achieved by the use of the present invention becomes a matter of prime importance in submarines.

A further advantage in connection with under water craft, derivable from the present invention is greater control in submerging and emerging. This facility can be obtained by locating the diving fins 54, 54' (Figs. 6 and 7) opposite the outlets 26e and 26'0 of the ducts I2C. 4The diving fins are thus disposed centrally of the current of water leaving the outlets, and said current as stated above, has, owing to its motion, a very high degree of consistency. Consequently, when the diving fin 54 is inclined (see Fig. 8) it acts to divert either upwards or downwards the emergent stream, the thrust of which against the main body of water therefore has its direction changed, so that it assists the motion of the vessel in the desired upward or downward direction.

If the ducts are fitted with water tight doors as described above, they may be used, in the case Of under water craft, as auxiliary or emergency emersion means. Suitable arrangements may be provided for evacuating the several compartments defined by the water tight doors, independently, so that, in case of need, additional .buoyancy may be provided at different parts along the length of the vessel. Should the normal tanks fail, the duct may be used to ensure that the vessel shall come to the surface, or the ducts may be utilised as accessories to the normal tanks to secure greater buoyancy should the vessel become entangled.

The inertia of the whirling columns of water in the ducts may likewise be vutilised to endow under water craft normally with a greater buoyancy than is at present customary, without the necessity for such a high percentage of submersion tanks, which in modern practice represent about a third of the under water body volume when the vessel is afloat. The reduction in the percentage of submersion tanks is made possible because even with a high buoyancy cceicient the vessel may be submerged by means of the diving fins, and when a sufficient depth has been obtained, the iins may be moved to a horizontal position without thereby causing the vessel to lose depth, inasmuch as the vessel will .be held at its submerged depth by reason of the stabilising effect of said whirling columns of water provided that the speed is maintained.

The above described advantages in the case of under water craft are of Vparticular interest in permitting improvements of design, lightening of the dead load, greater range of action and increased flexibility of control, al1 of which factors will greatly facilitate the task of the designer, and will enable him readily to design under water craft of tonnages three or four times as great as at present possible, for example submarine cruisers of high displacement.

For all classes of vessels, the present invention insures greater radius of action, increased stability, higher travelling speeds, a more efficient utilisation of space, and a greater ease in maneuvering. By suitably adjusting the pitch of the blades of successive screws, their relative speed of rotation and the direction of rotation of the screws in one duct as compared with that of those in another, the course of the vessel may readily be changed, and in fact, by reversingv the screws in one duct while continuing toy drive those in the other duct in the original direction, the vessel may be caused to swing round practically on itself. So great is the steering facility af forded by the novel propulsion means, that at least in some cases the normal rudders may be eliminated. Such facility of control and also other advantages above enumerated are of obvious importance in connection with fighting vessels.

It will be clear to those skilled in the art that in applying my invention in practice, I may introduce many and varied modifications without departing from the spirit and scope thereof, and consequently the invention is not intended to be limited tothe particular examples and embodiments hereinabove referred to but only as defined vin the appended claims.

a stern, and driving engines within the hull, im-

proved propulsion means comprising a pair of ducts arranged within said hull in parallel spaced ,Y

relationship at equal distances on either side of the longitudinal centre line of the ship, an enlarged intakelocated on one side of the bows and communicating with one of said ducts, a second enlarged intake located on the other side of the bows and communicating with the other duct, an outlet for said rst duct projecting beyond said hull at one side of the stern, a second outlet for the other duct extending through said hull on the other side of the stern, a first plurality of turbine screws disposed in spaced relation lengthwise of said rst duct and located therewithin, a second plurality 'of turbine screws disposed within said second duct in similar spaced relation longitudinally thereof, connecting means operatively connecting each of said screws individually to said engine, pitched blades on said screws, the pitch of the blades diminishing in successive screws from the bow end of the respective duct to the stern end thereof, the arrangement being such that said rst plurality of screws is normally driven -in a sense opposite to the sense of rotation of the second plurality of screws, and

.that the rotational speed of theV successive screws of either plurality increases from bow to stern, whereby a body of an aqueous medium in which the ship floats is adapted to be drawn into said duct and have imparted to it a whirling motion and an increment of kinetic energy as it passes within said duct from screw to screw, said body of medium being finally expelled from the other end of said duct. v

2; In a ship provided with improved propulsion means according to claim 1, watertight Anormally open doors operatively associated with said ducts and adapted upon closure to cut off communication between the aqueous medium and at least that portion of the ducts containing the screws, to permit of access to said screws for cleaning and repair.

3. In a ship provided with improved propulsion means according to claim 1, protecting grid-like structures located over said intakes to prevent the ingress of solid matter- JOS JUAN CORDOVA. 

